President Obama greets supporters at Bowling Green State University in… (Jewel Samad, AFP/Getty…)

CINCINNATI — Lori Monroe, a 40-year-old Democrat who lives in central Ohio, was startled a few weeks ago to open a letter that said a stranger was challenging her right to vote in the presidential election.

Monroe, who was recovering from cancer surgery, called the local election board to protest. A local tea party leader was trying to strike Monroe from the voter rolls for a reason that made no sense: Her apartment building in Lancaster was listed as a commercial property.

Monroe's is one of at least 2,100 names that tea party groups have sought to remove from Ohio's voter rosters.

The groups and their allies describe it as a citizen movement to prevent ballot fraud, although the Republican secretary of state said in an interview that he knew of no evidence that any more than a handful of illegal votes had been cast in Ohio in the last few presidential elections.

"We're all about election integrity — making sure everyone who votes is registered and qualified voters," said Mary Siegel, one of the leaders of the Ohio effort.

Some Democrats see it as a targeted vote-suppression drive. The names selected for purging include hundreds of college students, trailer park residents, homeless people and African Americans in counties President Obama won in 2008.

The battle over who belongs on the voter rolls in Ohio comes as supporters of Obama and his Republican challenger, Mitt Romney, are making elaborate plans to monitor the polls and mount legal challenges after the Nov. 6 election if necessary.

Obama's reelection campaign and Romney allies are already fighting in court over Republican efforts to block Ohio voters from casting ballots the weekend before the election. In 2008, Ohio's final weekend of early voting drew tens of thousands of African Americans to cast ballots, mainly for Obama.

The racial dimension of the 2012 clash over weekend voting burst into the open last month when one of Ohio's most powerful Republicans, Franklin County GOP Chairman Doug Preisse, told the Columbus Dispatch, "We shouldn't contort the voting process to accommodate the urban — read African American — voter-turnout machine."

Some Democrats see the developments in Ohio as part of a national drive by Obama's opponents to minimize turnout of his supporters, one that includes efforts elsewhere to impose new voter ID rules.

"Too much of this is going on for this not to be a coordinated effort," said Tim Burke, chairman of the Hamilton County Democratic Party in the tea party stronghold of southwestern Ohio.

The Rev. Rousseau A. O'Neal, one of a group of black ministers from Cincinnati who provided buses to take African Americans to the polls in 2008 and plan to do so again in November, described the tea party project and the curtailment of weekend voting as "bigotry of the highest order."

"Who ever thought we'd be fighting for the right to vote in 2012?" he asked.

The tea party groups, scattered around the state, have joined forces under the banner of the Ohio Voter Integrity Project. It is an offshoot of True the Vote, a Texas organization that has recruited volunteers nationwide to challenge voter rosters and work as poll watchers.

True the Vote was founded by Catherine and Bryan Engelbrecht, a couple who run an oil field equipment manufacturing firm in Rosenberg, Texas.

In Ohio, election records show, one of the project's top priorities has been to remove college students from the voter rolls for failure to specify dorm room numbers. (As a group, college students are strongly in Obama's camp.)

Voters challenged include 284 students at the Ohio State University campus in Columbus, 110 at Oberlin College, 88 at College of Wooster, 38 at Kent State — and dozens more from the University of Cincinnati, Miami University, Lake Erie College, Walsh University, Hiram College, John Carroll University and Telshe Yeshiva, a rabbinical college near Cleveland.

So far, every county election board that has reviewed the dorm challenges found them invalid.

In some cases, the Ohio tea party researchers have correctly identified voters who have died or moved, speeding up the official updating of registration files. They also found voters registered at a Cincinnati trailer park that no longer exists.

"We wouldn't know to take those folks off the rolls if it weren't for this project," said Alex Triantafilou, a Republican member of the Hamilton County Board of Elections.

Siegel, the Ohio project leader who is active in the Indian Hill Tea Party outside Cincinnati, called the project a nonpartisan attempt to ensure honest elections by cleaning up voter registration files. The project does not single out voters by race, party affiliation or neighborhood, she said.

All told, the Ohio group has questioned registrations in 13 counties, according to Siegel. In 2008, Obama won nine of them.